The proposed research can be divided into the following categories: 1) Basic design of the new total artificial heart (TAH) has proven to be satisfactory, but further improvements in the fabrication technique using either copolymer of silicone rubber and polyurethane or segmented polyurethane, will be done. Main improvements are focused on elimination of number of connections in assembly of the prosthetic device. 2) Durability test of the new heart will be performed 24 hours a day as soon as an extra control-driving unit becomes available on loan. 3) Performance test will be performed mainly in vivo experiments in relation to a mild exercise on a treadmill. 4) Major emphasis in pathophysiological studies will be given to studies on anemia, body fluid balance, and difference in response to exercise between the natural heart and TAH. Calorimetry and cardiovascular drug tests will be performed. Bibliographic references: Honda, T., Kito, Y., Gibson, W. H., Nemoto, T., Cockrell, J. V., and Akutsu, T.: One 25-day survivor with total artificial heart. J. Thor. Cardiov. Surg. 69:92, 1975. Honda, T., Kito, Y., Gibson, W. H., and Akutsu, T.: Akutsu total artificial heart; Part 2: Animal experiment and problems. Heart, 7:102, 1975 (Japan).